This invention relates to pressure gauges and in particular to gauges utilizing a helical bourdon tube as the pressure responsive element. Helical bourdon tubes are highly satisfactory for measuring relatively high pressures, such as 3000 psi, while being relatively small and requiring a small volume of fluid for operation.
Gauges of this type have been suggested for use in some analytical work, such as chromatography where it is desirable that the system be cleaned after each measurement to avoid contamination of succeeding samples by the residue of prior samples.
In the past, the conventional C-shaped bourdon tube has been provided with a plug or cap at the normally closed end for purging air or for cleaning. However this type of construction requires access to the tube for plug removal and replacement, and is not satisfactory for flushing on a regular basis. Also, the C-shaped tube requires in the order of one hundred times the volume of the helical tube for the same pressure and therefore is not suitable for most analytical instruments which have relatively small samples.
Accordingly, it is an object of the present invention to provide a new and improved pressure gauge with a helical bourdon tube as the pressure responsive element and having means for flushing the interior of the gauge including the tube from the external pressure line. A further object of the invention is to provide such a gauge which is simple and rugged in design, operable at relatively high pressure and requiring a relatively small volume of fluid for the pressure measurement.